1. Field of the Invention
The present invention relates to an active optical filter and, more particularly, to an active optical filter transmitting or blocking light according to whether a magnetic field is applied or not, and functioning as an optical filter transmitting light having a predetermined wavelength in accordance with an applied magnetic field.
2. Description of the Related Art
In general, in a color display device, a pixel is formed of three sub-pixels, each capable of expressing red, green or blue colors. Each sub-pixel includes a color filter transmitting only light of a corresponding color. Currently used color filters are passive filters transmitting only light having a predetermined wavelength, and do not function as an optical shutter which controls transmission or blocking of light. For example, an optical shutter of a liquid crystal display includes two polarization plates and a liquid crystal layer disposed between the polarization plates. In this case, light can be transmitted or blocked by controlling the crystal alignment of the liquid crystal layer using an electric field.
However, since an optical shutter having a complicated structure must be used in conjunction with a color filter, light loss in conventional color display devices is very large. For example, due to the light loss of the optical shutter and color filter, only 7-13% of light generated in a backlight unit can be delivered to the viewer.